Systems and methods for producing and delivering ultrasonic therapies for wound treatment and healing

ABSTRACT

One embodiment is directed to a non-contact, medical ultrasound therapy system for generating and controlling low frequency ultrasound. The ultrasound therapy system includes a treatment wand including an ultrasonic transducer, a generator unit, and a cable coupling the treatment wand to the generator unit. The generator unit generates electric power output to drive the ultrasonic transducer and includes a digital frequency generator, wherein the generator unit digitally controls energy output at resonance frequency of the ultrasonic transducer.

RELATED APPLICATION

This application is a continuation of application Ser. No. 14/546,808filed Nov. 18, 2014, which claims the benefit of U.S. Provisional PatentApp. No. 61/909,086 filed Nov. 26, 2013, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Embodiments relate generally to ultrasound therapy systems and methodsand more particularly to a non-contact, low-frequency, highly efficientultrasound therapy system that delivers ultrasonic therapy treatmentsvia a mist to a patient wound to promote wound healing.

BACKGROUND

Use of ultrasonic waves to promote healing of wounds has become morecommon in recent years as its benefits are better understood and thistype of therapy becomes more widely utilized. In general, ultrasonicwaves have been used in medical applications for a long time, includingdiagnostics, therapy, and industrial applications.

A number of innovative ultrasound therapy systems and devices havepreviously been developed including non-contact, ultrasound mist therapydevices by the assignee of the current application, Celleration, Inc.These systems and devices have been widely used for medical treatmentsin medical facilities around the world. See, for example, co-owned U.S.Pat. No. 6,569,099, entitled ULTRASONIC METHOD AND DEVICE FOR WOUNDTREATMENT, which is incorporated herein by reference in its entirety.Unlike most conventional wound therapies that are limited to treatmentof the wound surface, Celleration, Inc., developed therapies in whichultrasound energy and atomized normal saline solutions were used tostimulate the cells within and below the wound bed to aid in the healingprocess.

Although these ultrasound therapies have been effective, devices,systems and methods providing improved ultrasonic therapies that aremore accessible, safer to administer to patients, and more efficient indelivery of ultrasound energy have been widely desired.

SUMMARY

Embodiments relate to non-contact, low-frequency, highly efficientultrasound therapy devices, systems and methods that deliver ultrasonictherapy treatments via a mist to a patient wound to promote woundhealing. One embodiment is directed to a non-contact, medical ultrasoundtherapy system for generating and controlling low frequency ultrasound.The ultrasound therapy system includes a treatment wand including anultrasonic transducer, a generator unit, and a cable coupling thetreatment wand to the generator unit. The generator unit generateselectric power output to drive the ultrasonic transducer and includes adigital frequency generator, wherein the generator unit digitallycontrols energy output at resonance frequency of the ultrasonictransducer.

Another embodiment is directed to a highly efficient ultrasonicgenerator unit. The ultrasonic generator unit includes an ultrasonicdriver with digital controls to maintain system displacement atresonance frequency of a transducer coupled to the ultrasonic generatorunit. The ultrasonic driver in this embodiment includes amicroprocessor, a digital frequency generator, and a phase detector.

A further embodiment is directed to an ultrasonic system. The ultrasonicsystem includes a user interface controlled by a first microprocessor, atreatment device including an ultrasonic transducer, and a generatorunit including an ultrasonic driver controlled by a secondmicroprocessor. In this embodiment both the first microprocessor and thesecond microprocessor are configured to individually suspend operationof the ultrasonic system in fault condition situations.

A further embodiment is directed to a method for digitally generatingand controlling low frequency ultrasound used in a non-contact medicalultrasound therapy system. The method includes performing a power onself-test to an ultrasonic therapy system that includes a treatment wandcontaining an ultrasonic transducer and a generator unit containing anultrasonic driver. The method further includes performing a frequencysweep using a sine wave to determine a resonance frequency of theultrasonic transducer by evaluating and looking for a relative minimumimpedance of the ultrasonic transducer. The method further includesadjusting the digital frequency generator output frequency based onvoltage vs. current phase angle so that a frequency lockup is maintainedat the resonance frequency, and monitoring voltage and phase detectioncircuits of the ultrasonic therapy system for phase difference.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is an ultrasound device of a system providing non-contact therapyto patient wounds via a low frequency ultrasound mist, according to anembodiment.

FIG. 2 is a diagram of an ultrasound therapy system, according to anembodiment.

FIG. 3 is a diagram of an ultrasound therapy system, according to anembodiment.

FIG. 4 is a diagram of an ultrasound device of a system providing fornon-contact therapy to patient wounds via a low frequency ultrasoundmist, according to an embodiment.

FIG. 5 is a diagram of the interaction of the DDS (Direct DigitalSynthesis) feature and microprocessor that provides digital frequencygeneration, according to an embodiment.

FIG. 6 is a diagram of the frequency control loop of the system,according to an embodiment.

FIG. 7 is a diagram of the constant current control loop of the system,according to an embodiment.

FIG. 8 is a graph of an example of impedance versus frequency, in anultrasonic transducer device, according to an embodiment.

FIGS. 9a-9g show a diagram of the operation of the ultrasonic therapysystem, according to an embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

Various embodiments may be embodied in other specific forms withoutdeparting from the essential attributes thereof, therefore, theillustrated embodiments should be considered in all respects asillustrative and not restrictive.

A need for a more accessible and safer ultrasonic therapy device andsystem for patients to use has been recognized in this disclosure.Further, many of the substantial technical obstacles to providing such adevice based on the requirements of conventional ultrasound therapydevices are recognized and overcome by this disclosure. Specifically,making devices more readily accessible to additional patient populationshas been a significant problem due to the very high voltage necessary tooperate conventional devices. For example, some conventional ultrasoundtherapy devices have operated at about 700 Volts (V) peak-to-peak and 7Watts (W) of energy. This has necessitated qualified oversight oftherapy provision, as allowing patients to operate such a high voltagemachine on their own might otherwise present a significant safety risk.Further, the energy requirements of conventional devices have made thepossibility of a portable battery powered device, which could be used ina homecare environment, unfeasible. Ultrasound therapy systems describedherein, however, overcome many or all of the technological obstacles ofthe past and provide a lower-power, safer, more efficient, and moreaccessible ultrasound therapy system. In embodiments, an ultrasoundtherapy system can be monitored and controlled to operate at or nearresonant frequency (Fr), which can be more efficient that operating ator near anti-resonant frequency because it requires less voltage and ismore efficient. Even battery powered systems are possible in certainembodiments. Accordingly, designs for new medical ultrasound devices,systems and methods incorporating various features, concepts andimprovements, are described in the following detailed description.

FIG. 1 shows an example of a medical ultrasound device 20 of anultrasound therapy system 10 (refer, e.g., to FIG. 2) for deliveringnon-contact ultrasound therapies to patient wounds via a low-frequencyultrasound mist. Medical ultrasound device 20 comprises both aconsole/generator unit 30 for generating power and a treatment wand 40for administering therapies. In general, generator unit 30 suppliespower to an ultrasonic transducer within the treatment wand 40.Treatment wand 40 is ergonomically designed and can be generallypistol-shaped such that it may be conveniently positioned by a user todirect ultrasonic energy to a treatment area via atomized saline mistemitted from the end of treatment wand 40. Treatment wand 40 also can bebalanced, such as in its physical design and weight distribution, tofurther improve and enhance ergonomics and usability. Generator unit 30further comprises an external pump 50 which pumps saline or other fluidthrough a tube (not shown) attached to the end of treatment wand 40.Pump 50 depicted in FIG. 1 is a peristaltic pump but can compriseanother suitable pump type or mechanism in other embodiments.

FIGS. 2 and 3 show high-level block diagrams of components of ultrasoundtherapy system 10. In general, as depicted in FIG. 2, system 10comprises generator unit 30; treatment wand 40; fluid management pump50; an ultrasonic driver 60; an ultrasonic transducer 70; and anapplicator 80.

Generator unit 30 and treatment wand 40 are connected by a cable 90.Ultrasonic driver 60 comprises hardware mounted inside generator unit30. A basic function of the ultrasonic driver 60 is to generate electricpower output to drive ultrasonic transducer 70. Ultrasonic transducer 70includes an acoustic horn 100 and related assembly mounted insidetreatment wand 40. Ultrasonic transducer 70 converts and transfers inputelectrical power into vibrational mechanical (ultrasonic) energy thatwill be delivered to the treatment area (i.e. to a patient wound areavia atomized saline). Treatment wand 40 contains the system's userinterface 110 and controls for parameters of the treatment, though inother embodiments an additional or alternative user interface can beincorporated in generator unit 30. Treatment wand 40 is configured toappropriately position and hold applicator 80 relative to acoustic horn100 for proper delivery of fluid during operation. The configurationalso provides appropriate atomization of saline fluid and delivery ofthe resulting mist and ultrasound energy to a wound treatment area.

Fluid management pump 50 provides a fixed flow rate of saline or otherfluid (e.g., about 0.9% normal saline in one embodiment) via a tube 120to the distal tip 140 of ultrasonic transducer 70 from a saline bag 130or other source, as appropriate. The saline fluid is delivered to theradial surface of transducer horn near its tip 140. The saline fluid isdispensed through an orifice on a superior surface of the horn 100, anda portion of the saline is displaced forward to the face of horn 100 andatomized by horn 100 when it is energized and operating. The remainingvolume of fluid is fed to an inferior surface of ultrasonic transducer70 via gravity and capillary action. When a sufficient volume of salineis accumulated, transducer tip 140 atomizes the saline into a plume. Theatomized saline spray plume emanates from two points on the ultrasonictransducer 70, i.e., generally at the 12 o'clock and 6 o'clock positionsgiven normal positioning of treatment wand 40 in operation, formingintersecting spray paths at approximately 5 mm from the front face ofultrasonic transducer 70 in some embodiments. In other embodiments,treatment wand 40, transducer 70, horn 100, tip 140 and/or othercomponents can be designed to provide a differently sized or configuredspray plume and paths.

FIG. 4 is a block diagram of a more detailed schematic of generator unit30 and treatment wand 40 of ultrasound device 20. As can be understoodfrom the following description, parameter control of voltage, current,duty cycle and phase angle is enabled, in some embodiments.

Treatment wand 40 houses ultrasonic transducer 70 and includes amicroprocessor 200, various interface and sensing components, and anOLED display 206. Treatment wand 40 is pistol-shaped in embodiments toprovide an improved ergonomic operator design, though otherconfigurations can be implemented as may be advantageous in someapplications. Treatment wand 40 comprises an acoustic horn assembly(e.g., piezo elements, back mass, horn and booster), ultrasonictransducer 70, microprocessor (MCU2) 200, user control key pad 202 andtrigger 204, and an LCD screen display 206 that displays operationalinformation and enables control and programming of the treatment therapy(see, e.g., FIG. 1). Treatment wand 40 also includes an RFID transceiver208 in some embodiments, and RFID transceiver 208 can be used toidentify applicator 80. This feature can be used to ensure that there isonly a single use of a particular applicator 80 and to thereby deterunwanted reuse across multiple patients and/or treatments. Treatmentwand 40 connects to generator unit 30 through cable 90. Cable 90includes ultrasonic driver output power, communication components (suchas those compatible with RS485, RS422 and/or other protocols) and powercomponents (such as +5V and ground) in an embodiment, though other powerand/or communications features can be implemented or facilitated bycable 90 in other embodiments. In one embodiment, 3.3V and 12.9V powercan be generated from the 4.5V power provided by generator unit 30 forthe electronics in the treatment wand 40. These example powercharacteristics can vary and are merely examples of one embodiment.

User interface 110 on treatment wand 40 includes key pad 202, trigger204, and screen display 206. In some embodiments, display 206 can be afull-color OLED display, and key pad 202 can be a four button display,as shown in FIG. 1. The operator can configure and control device andsystem operation via key pad 202 and initiate the delivery of therapiesby depressing a trigger switch 204.

Microprocessor 200 that controls user input requirements can alsomeasure the internal temperature of treatment wand 40, or of transducer70 or horn 100 more specifically, from ultrasonic transducer sensor 210and treatment wand sensor 212. Microprocessor 200 also sends read/writeinformation to applicator 80. Microprocessor 200 communicates withgenerator unit 30 via a communications protocol transceiver 214 (such asone compatible with RS485, RS422 and/or other protocols) and writesinformation to memory 216, which can be EEPROM, serial flash, or someother suitable memory. This information is stored and can be retrievedfor understanding the use and performance of the system. Accordingly,greater detail can be given on data stored, how much, how long and howretrieved (USB upload/download by the user, service or other).

RFID transceiver 208 of treatment wand 40 can be used to communicatewith an RFID tag (not shown) for applicator detection, as previouslymentioned. The RFID tag can be located on applicator 80, andmicroprocessor 200 in treatment wand 40 can serve as an RFID reader andwriter of the signals received via RFID transceiver 208. Specifically,an RFID controller can be used in treatment wand 40 for a Read/Write RFtag on applicator 80. In each new treatment, system 10 will require anew applicator 80. The RFID controller can read the ID tag of applicator80 to identify if that particular applicator 80 is new or used. After aparticular applicator 80 is used for a specified period of time, theRFID controller can write the information to an ID tag to identify thatapplicator 80 has been used to avoid reuse.

Microprocessor 200 of treatment wand 40, or another component of system10, can be used to control input and output functions and performcontrol loops and calculations. Features of microprocessor 200 oranother microprocessor or component of system 10 in some embodiments caninclude: an 80 MHz maximum frequency; 1.56 DMIPS/MHz (Dhrystone 2.1)performance; an operating voltage range of 2.3V to 3.6V; a 512K flashmemory (plus an additional 12 KB of Boot Flash); a 128K SRAM memory; aUSB 2.0-compliant full-speed device and On-The-Go (OTG) controller; upto 16-channel, 10-bit Analog-to-Digital Converter; six UART modules withRS-232, RS-485 and LIN support; and up to four SPI modules. Thesefeatures are merely examples of one embodiment and can vary in otherembodiments.

Ultrasonic transducer 70 generally comprises a piezoelectric ceramicelement and metal horn 100 mounted in a sealed housing. The ultrasonictransducer input can be an AC voltage or AC current, or an AC voltagethat results in a current, and the waveform can be a square form or sineform. The ultrasonic transducer output is mechanical vibration of thetip of transducer 70. The amount of energy output depends on tip 70displacement, frequency, size and driver load (e.g., air or liquidmist). The ratio of output to input energy is referred to as theelectromechanical coupling factor. There are many variables that affectcoupling factor, including frequency. In theory, it can be advantageousto operate an ultrasonic transducer (sometimes referred to as UST) bykeeping the operating frequency in the resonant frequency (Fr) oranti-resonance frequency (Fa) region. At Fr, the electrical power factoris 1, while near or approaching Fr the power factor only approaches 1.However, due to the related, very unique impedance-frequencycharacteristics of transducers, which can vary from transducer totransducer, drive circuit design is very difficult. In previouslydesigned ultrasonic drivers, Phase Loop Lock (PLL) techniques werewidely used. Because of the nature of analog performance, keeping ahighly accurate and stable frequency output was very difficult. Intheory, an ultrasonic transducer that operates at Fr or Fa has a highefficiency output. In practice, operating a UST at Fr or Fa can bedifficult or impossible with PLL technology. This is why most ultrasonicdrivers with a PLL design only can operate in Fr or Fa regions ratherthan at Fr or Fa points, and the operational phase typically may be morethan 50 degrees. For most systems with rapidly changing load impedance,operation at frequencies close to Fa or Fr will cause the system to beunstable. Alternatively, a system can be kept stable by setting theoperation frequency lower than Fr or higher than Fa points, so long asthe frequency does not drift to a resonant point. In embodimentsdiscussed herein, however, the ultrasonic driver can be monitored andcontrolled to operate at or very near Fr, a significant advantage overconventional systems.

In embodiments, Fr and Fa can be equated or analogized with serial andparallel, respectively, resonance frequencies. This is shown in Table 1:

TABLE 1 V/I Phase = 0 degrees Defined Impedance = Minimum Impedance =Maximum Mechanical Resonance Anti-resonance frequency (Fr) frequency(Fa) Electrical Serial resonance frequency Parallel resonance frequencyV/I phase = 0 degrees V/I phase = 0 degrees Ultrasound ZFr = minimumsystem 10 and Phase = 0 degrees Frequency = 39 kHz~41 kHz

Ultrasonic transducer 70 is operated at relatively large displacementsand a low load variation, thereby reducing loading effects andelectrical impedance. Accordingly, ultrasonic medical applications canuse a constant current control algorithm to achieve one or more of thefollowing performance advantages: increased electrical safety due tolower operating voltage; lower operating voltage by running at Fr;proportional current to maximum tip velocity (displacement if frequencyis held constant); tip displacement proportional to current; and thecapability to limit excessive power surges by setting the voltage railto an appropriate value, among others.

Generator unit 30 includes a power entry module and AC/DC power supply300 as well as an ultrasonic driver 60. Delivery pump 50 is mounted ongenerator unit 30 and is controlled by a pump driver located onultrasonic driver 60. Communications ports 302, 304, and 306 are alsolocated on the generator unit 30, though the number and arrangement ofcommunications ports can vary from those depicted. For example, in otherembodiments more or fewer ports are provided, and one or more of theports can comprise a wireless communications port (e.g., infrared, RF,BLUETOOTH, WIFI or some other wireless technology). These ports providean information exchange between generator unit 30 and treatment wand 40as well as information exchange between device 20 and user.

With respect to the Power Entry Module & AC/DC Power Input, in someembodiments the local AC MAINS is connected to an appliance inlet with ahospital grade detachable power cord. In some embodiments, differenttypes of power cords can be used: 15 A with a 125V rate, or 10 A with a250V rate. In some embodiments, the appliance inlet is a power entrymodule listed for medical applications with an 10 A current rating,120/250 VAC voltage input, MAINS switch, integral fuse holder(2¼×1¼″/5×20 mm fuses), EMC line filter for medical applications, and ismounted on the rear panel of the chassis. Although not depicted in thefigures, embodiments are contemplated that use battery power as thepower source in the system's design. The battery would be located withingenerator 30 in various embodiments. Battery power is made possible dueto the extremely efficient design discussed herein.

In some embodiments, system 10 can have a universal AC power inputcapability accepting a range of power input from 90V to 265 VAC. Thelocal AC MAINS are connected to an appliance inlet component (IEC 320C14) with a hospital grade detachable power cord. The appliance inlet isa power entry module listed for medical applications with an 115V/230Vvoltage input, MAINS switch, integral fuse holder (2-5×20 mm fuses), andan EMC line filter for medical applications that is mounted on the rearpanel of the chassis. The MAINS switch output is connected to two AC/DCswitching power modules. The two AC/DC (24V output) switching powersupply modules provide +/−24V power to class-AB type amplifier use. AllDC power sources +5V, +4.5V, −4.5V and 3.3V can be generated from a +24VDC power source via DC/DC converter. The +5 VDC will provide 5V powerto treatment wand 40 through the detached cable and medical gradeconnector 90. While class-AB amplifiers are mentioned in examples hereand elsewhere, in embodiments class-D or other amplifiers also can beused.

In some embodiments, two identical AC/DC (24V output) switching powersupply modules are serially connected together to provide +/−24V powerto class-AB type amplifier use. The power supply can be medical grade,Class II, BF rated with 45 W output with conventional cooling. A dualcolor (Red/Green) LED 308 can be mounted at the front of generator unit30. The green color indicates normal power on without errors, and thered color indicates a system error or failure. Error detail informationcan also display on the interface display screen 206 of treatment wand40.

In some embodiments, there is a plurality of, such as three,communication ports in the on generator 30. The first port is acommunication port 302 (such as one compatible with RS485, RS422 and/orother protocols), with 5V power and UST outputs. This port 302 isconnected to treatment wand 40 through cable 90. Port 302 can beconfigured for full duplex communications in both directions at the sametime. This port 302 can handle information exchange between generatorunit 30 and treatment wand 40. In operation, both sets ofmicrocontrollers 200 and 316 can check each other to ensure none hasfailed to operate through this port 302. The second port can be a USB-2type A port, referred to herein as port 304. It can be designed for userdownload of information stored at the memory 310, which can compriseEEPROM, serial flash, internal non-volatile, or other suitable memory,by using a flash key or other device. This port 304 can be used foruploading software from flash key device. A third port can be anRS232-3.3V serial port, referred to herein as port 306. Port 306 can bedesigned for use with a PC, so the PC can communicate to the system 10for download, upload, system debug and calibration. Also included ingenerator unit 30 and connected to the microcontroller are RTC atnumeral 305, an audible signal generator 307 and generator temperaturesensor 309, though in embodiments one or more of these features can beomitted or relocated. For example, in one embodiment audible signalgenerator 307 can be located in treatment wand 40 instead of or inaddition to being in generator unit 30.

A microcontroller controlled pump delivery system 312 can be used forfluid delivery. Delivery system 312 comprises a pump 50 and pump driverwith controls 314 for pump speed and pump door monitoring and candeliver fluid, such as saline, through a tube 120 and applicator 80 tothe tip of ultrasonic transducer 70. Microcontroller (MCU1) 316 ofgenerator unit 30 can control peristaltic pump speed to control salineflow rate for a fixed tubing size. Pump delivery system 312 generallyoperates at constant flow rate for all operating conditions. A coolingfan 317 is mounted in the back of generator unit 30. It is controlled bymicrocontroller 316 of ultrasonic driver 60.

Ultrasonic driver 60 includes a microprocessor 316 that controls,measures and monitors the drive electronics and communicates with thehardware and software of the treatment wand 40. In some embodiments,ultrasonic driver 60 includes a microprocessor 316 (such as MicrochipTechnology Inc. PIC32) with an 80 MHz clock and 1.56 DMIPS/MHzperformance, though some other suitable microprocessor can be used inother embodiments. The drive electronics contain a digital frequencygenerator (DDS) 318, AC amplifier 320 and voltage and current peakdetection circuits 322 and 324. Digital frequency generator 318generates accurate frequencies set by microprocessor 316 to AC amplifier320 that are output to ultrasonic transducer 70. In some embodiments, ACamplifier 320 can be coupled to impedance matching circuitry 326, thoughin other embodiments this circuitry 326 can be omitted or implemented insoftware or firmware rather than hardware. Voltage and current peakdetection circuits 322 and 324 continually monitor the signal peaks withphase difference sensed at 328. In some embodiments, internal orexternal timers can be used to monitor phase difference or in themonitoring of phase difference. In operation, microprocessor 316 canadjust the digital frequency generator output frequency based on voltagevs. current phase angle so that the frequency is locked at the resonancefrequency Fr of ultrasonic transducer 70. The resonance frequency Fr isnot a fixed frequency, however, as it can drift with temperature andother changes. This is discussed herein below in additional detail.

Ultrasonic driver 60 includes a digital frequency generator 318, aresonance frequency control loop 400, and an output current control loop500. Microcontroller 316 can be of sufficiently high speed so as tohandle all input measurements and output settings, especially for phasecomparison of cycle by cycle frequency adjustment in real time.Ultrasonic driver 60 generates electrical output with an ultrasonicfrequency and a required power.

At Fr and Fa, the impedance phase is 0 degrees, which means thatultrasonic transducer 70 can achieve the highest power efficiency atthose points. Accordingly, it is recognized that keeping the outputfrequency close to Fr or Fa would be desirable, if possible. However, itis very difficult for any control systems to operate at Fr and Fa, as atthose points any small increase or decrease of frequency will cause alarge impedance increase or decrease. Accordingly, most ultrasonicdrivers either operate at frequencies higher than Fa or lower than Frbecause frequencies are relatively stable when they are farther from Fror Fa.

For example, some conventional systems have been designed to operate inthe Fa region. These designs were relatively stable and deliveredeffective treatment, but output power efficiency was very low and a veryhigh operating voltage was required. Accordingly, in order to meetregulatory safety requirements, wires with high isolation and earthprotection were required, adding cost and restricted user ergonomics dueto a stiffer and heavier cable.

An example comparing the voltage required by a past device operating atFa compared to an embodiment of the currently disclosed system,operating at Fr, is set forth below:

A conventional ultrasonic transducer was operated at, or above,anti-resonance, which is approximately 1 KΩ˜8 KΩ impedance. To deliverthe required power to the transducer the driver must output very highvoltage (300V) to the transducer. The power calculation is:

P=I ² Z*Cos φ  Equation 1

-   -   P: input power of transducer    -   I: input current    -   Z: transducer impedance in Ohm    -   φ: voltage vs. current phase angle (−90°˜+90°)        If the transducer requires 7 W power, φ=85°, Z=1500Ω, from        Equation 1 the current will be:

$I = {\sqrt[2]{\frac{P}{Z*{Cos}\; \phi}} = {\sqrt[2]{\frac{7\; W}{1500\Omega*{{Cos}( {85{^\circ}} )}}} = {230\mspace{14mu} {mA}}}}$

Accordingly, a power supply voltage would be: (230 mA*1500Ω)=345V.

An embodiment of system 10, in contrast, operates at Fr with constantcurrent output control. Its impedance is about 25˜80Ω and voltage vs.current phase angle close to 0 degrees. The power efficiency is almost100%. An example with Fr impedance is 50Ω.

If the transducer requires 7 W power, φ=0°, Z=50Ω, the current will be:

$I = {\sqrt[2]{\frac{P}{Z*{Cos}\; \phi}} = {\sqrt[2]{\frac{7\; W}{50\Omega*{{Cos}( {0{^\circ}} )}}} = {370\mspace{14mu} {mA}}}}$

and the power supply voltage will be: 370 mA*50Ω=18.7V

Accordingly, embodiments of system 10, with a low voltage operationcondition, can be much more efficient and safer than conventionaldesigns. Any voltage surges resulting when transducer impedance isincreased can be limited by setting the voltage rail to an appropriatevalue.

Microcontroller 316 of the ultrasonic driver controls all input andoutput functions and performs all control loops, calculations.Embodiments of microcontroller 316 can include one or more of thefollowing: a 80 MHz maximum frequency; 1.56 DMIPS/MHz (Dhrystone 2.1)performance; an operating voltage range of 2.3V to 3.6V; a 512K flashmemory (plus an additional 12 KB of Boot Flash); a 128K SRAM memory; USB2.0-compliant full-speed device and On-The-Go (OTG) controller; up to16-channel, 10-bit Analog-to-Digital Converter; six UART modules withRS-232, RS-485 and LIN support; and up to four SPI modules. Thesecharacteristics are merely examples and can vary in other embodiments.

The ultrasonic frequency generator is a digital frequency generator 318that provides numerous advantages over conventional designs. In someconventional designs, PLL technology was used with or comprises part ofa voltage control oscillator (VCO) for generating a fixed ultrasonicfrequency. However, this produced an output frequency that is lowresolution and not flexible for wide frequency range applicationswithout hardware changes. Further, the frequency stability was imprecisesince the VCO is affected by temperature, noise and power ripple.

In the current ultrasonic therapy system 10, a Direct Digital Synthesisprogrammable frequency generator (DDS) is used as part of the frequencygenerator 318. Because a DDS is digitally programmable, the outputfrequency can be easily adjusted over a wide range. DDS permits simpleadjustments of frequency in real time to locate resonance frequencies orcompensate for temperature drift. The output frequency can be monitoredand adjusted based on phase difference measurements in embodiments, andcan be continually adjusted by microcontroller 316 at real time speed.Advantages of using DDS to generate frequency include: digitallycontrolled sub-Hertz frequency-tuning resulting in sub-degreephase-tuning capability; extremely fast speed in tuning output frequency(or phase); and phase-continuous frequency hops with noovershoot/undershoot or analog-related loop setting-time anomalies,among others. In embodiments, a sine-wave output can be generated by theultrasonic transducer, which can provide cleaner signals to sensingcircuitry. Additionally, because the voltage and current maintain a veryclose semblance of a sine wave, peak sensing can be used withoutrequiring more elaborate true Root Mean Square (RMS) conversion.

The digital architecture of DDS eliminates the need for the manualtuning and tweaking related to components aging and temperature drift inanalog synthesizer solutions, and the digital control interface of theDDS architecture facilitates an environment where systems can beremotely controlled and optimized with high resolution under processorcontrol. FIG. 5 shows the system's digital frequency generation usingmicrocontroller 316 and DDS 318. Specifically, frequency set 370 andamplitude set 372 are received by DDS 318 which generates an outputfrequency 374 (f_(out)).

FIG. 6 sets forth the frequency control loop 400 for system 10.Frequency control loop 400 includes a digital frequency generator (DDS)318, D/A converter 378, phase detector 380 and microprocessor 316. Thedrive electronics utilize the digital frequency generator 318, ACamplifier 320 and voltage and current peak detection circuits 322 and324. Digital frequency generator 318 generates a high accuracy andprecision frequency signal, set by the microprocessor 316, to ACamplifier 320 that outputs across a transducer load 382 to ultrasonictransducer 70. At start-up, system 10 performs a Power On Self-Test(POST) and communicates with ultrasonic transducer 70 to gatherinformation on characteristics of ultrasonic transducer 70 and determinethat treatment wand 40 is functioning properly.

Specifically, when initially energized, microprocessor 316 can beprogrammed to perform a frequency sweep using a sine wave to determinethe resonant frequency by evaluating and looking for a relative minimumimpedance of ultrasonic transducer 70. The sweep is confined to asmaller defined interval based on the information embedded in treatmentwand 40 regarding the operating characteristics of ultrasonic transducer70. This includes the information stored about ultrasonic transducer 70at the time of manufacture or otherwise programmed or updated. Duringthe system start, digital frequency generator 318 can scan frequenciesfrom a start frequency (min 20 KHz, adjustable) to an end frequency (max50 KHz, adjustable) to find the resonance frequency (Fr). Microprocessor316 can adjust the digital frequency generator output frequency based onvoltage vs. current phase angle so that the frequency lockup ismaintained at the resonance frequency of ultrasonic transducer 70 (i.e.,at a 0° phase angle). Because the frequencies continually shift due totemperature change and other factors, the phase of output voltage andcurrent will change as well. The voltage vs. current phase detectioncircuits are continually monitored for the phase difference and thefrequency adjusted accordingly. Resonance frequency is not a fixedfrequency. This is due to heating and other factors causing a slightdrift change with temperature. Specifically, increased temperature cancause decreased resonant frequency.

In order to keep output frequency lockup at resonance frequency,frequency control loop 400 can monitoring output voltage vs. currentphase angle in real time and continually adjust operating frequency tomatch the current resonance frequency. In some embodiments,microprocessor 316 can maintain Δφ (as illustrated at 390) to less thanabout 0.1 degree inaccuracy and provide sufficient capabilities toachieve accuracy of about 0.1 Hz or better. In some embodiments,resonance frequency is digitally controlled to better than about 0.5 Hzwhile maintaining constant energy output.

FIG. 7 sets forth output current control loop 500 for system 10. Outputcurrent control loop 500 is designed to provide a constant currentoutput. Since the transducer output displacement is a function oftransducer drive current, the control output current (not voltage) willcontrol output displacement. Displacement, of a given tip area,determines the amount of ultrasound energy delivered/output.Microprocessor 316 monitors the output current via a sensing resistorthen adjusts the digital frequency generator 318 output signal level tomaintain constant current output thus maintaining a constant outputdisplacement from the tip of the horn. Current sensing circuit 322 cansense peak current, and in some embodiments, such as for data loggingformat output or other purposes, convert peak value to an RMS value. Anywaveform distortion can cause converter errors, causing current controlerrors and ultimately displacement errors. To avoid this situation,embodiments of the system can use RMS sensing technology to reduce theerrors. This can be implemented if the waveform has considerabledistortion, for example.

In system 10, the digital frequency generator 318 can be used to allowfor selection and use of different frequencies via softwareimplementation. Configurations having operating frequencies ranging fromabout 20 kHz to about 50 kHz are possible. Digital frequency generator318 is digitally programmable. Accordingly, the phase and frequency of awaveform can be easily adjusted without the need to change hardware(frequency generating components), unlike VCO or PLL based generators,as would normally be required to change when using traditionalanalog-programmed waveform generators. Digital frequency generator 318permits simple adjustments of frequency in real time to locate resonancefrequencies or compensate for temperature drift or other deviations inthe resonant frequency. The output frequency can be monitored via phasedifference measurements and continually adjusted by microcontroller 316at real time speed.

There are many advantages to using digital frequency generator 318 togenerate frequency. For example, this provides a digitally controlled,0.01-Hertz frequency-tuning and sub-degree phase-tuning capability aswell as extremely fast speed in tuning output frequency (or phase). Thedigital frequency generator 318 also provides phase-continuous frequencychange with no overshoot/undershoot or analog-related loop setting-timeanomalies. The digital architecture of the digital frequency generator318 eliminates the need for the manual tuning and tweaking related tocomponents aging and temperature drift in analog synthesizer solutions,and the digital control interface of the digital frequency generatorarchitecture facilitates an environment where systems can be remotelycontrolled and optimized with high resolution under processor control.

In this system, ultrasonic driver 60 outputs a sine waveform through aclass AB power amplifier 320. It can operate at frequency from 20 KHz to50 KHz, constant current mode. The ultrasonic driver 60 outputs currentfrom 0 to 0.65 A, voltage from 0 to 30 Vrms, Max power to 19.5 W, inembodiments, though these values and ranges can vary in otherembodiments. The ultrasonic driver output can scan resonance frequenciesfrom the 20 KHz to 50 KHz range, detect minimum impedance (0° degreephase angle of voltage vs. current), and then lock operational frequencyto resonance frequency of the ultrasonic transducer 70 at a ±0.5 Hzaccuracy level. Parameters may vary in various embodiments. In certainembodiments, the drive voltage requirements are less than 50 Vrms forthe system.

The technology of system 10 is unique in that it sees an essentiallyconstant load. The no-load condition is similar to the operational load.Being a non-contact treatment and dispensing only a small amount offluid onto the horn does not create a significant variation in theload/output, allowing the system to be run at resonance (Fr). Runningand controlling the system at Fr allows improved efficiency, aspreviously discussed. Typical ultrasound applications such as welding,mixing, cutting, and cleaning have significant variation in the load,e.g., going from a no-load to full load condition. The variation makescontrol of the output very difficult and requires greater power at thecost of efficiency.

FIG. 8 is a graph that helps to illustrate advantages of using system10's ultrasonic driver based on the impedance and frequencycharacteristics of ultrasonic transducer 70. Specifically, the dramaticchange in impedance magnitude 602 and phase 604 is seen for changes infrequency 606 for even small deviations from the resonance frequency 608and anti-resonance frequency 610. Ultrasonic transducer 70 is acomponent that converts electrical energy to mechanical energy. Itsimpedance and frequency characteristics create significant drive circuitdesign challenges, especially if trying to optimize for low power inputand accuracy. Traditional ultrasonic driver designs typically use PhaseLoop Lock (PLL) frequency control technology. However, analog systemperformance generally does not allow for accuracy and stable frequencyoutput. Accordingly, this can make it difficult to control the systemprecisely with analog systems. In theory, an ultrasonic transduceroperating at resonance frequency Fr or anti-resonance Fa frequency has ahigh efficiency output. In practice, when ultrasonic transducers operateat resonance frequency or anti-resonance frequency, it is almostimpossible using PLL technology to maintain elegant control. Typicalultrasonic drivers utilize an analog PLL based design for control. ThePLL based designs operate close to resonance frequency or anti-resonancefrequency points, but due to their inherent inaccuracy, these oftenoperate at some phase angle away from Fr or Fa leading toinefficiencies.

In system 10, a constant current control algorithm can be used. It canoperate at resonance frequency, rather than just close to resonantfrequency. The difference between anti-resonance and resonance is thatat anti-resonance the system can operate with high impedance and atresonance with lowest impedance. The high impedance can be in the rangeof about 5 KΩ to about 50 KΩ, and low impedance can be in a range ofabout 20Ω to about 100Ω in certain embodiments, for example.

Since ultrasonic transducer 70 is operated with relatively largedisplacements and a low load variation, there is a significant reductionin loading effects and electrical impedance variation. Many ultrasonicmedical applications use a constant current control algorithm because ofthe following performance advantages: electrical safety (such as due toa lower operating voltage); current that is proportional to frequencyand/or maximum tip velocity (displacement if frequency is heldconstant); fewer excessive power surges (by setting and maintaining thevoltage rail to an appropriate value); and the ability to monitor andcontrol displacement of the tip.

Some embodiments of system 10 have three modes of operation: a TREATMENTmode; an INFORMATION mode; and a TERMINAL mode. If the user enters theTREATMENT or normal operating mode upon power up, the user can selectthe length of time for a treatment and energize the acoustic output totreat a patient. If the INFORMATION mode is entered on power up with aflash key plug to the USB port, user information can be downloaded thathas been stored in the memory to flash or new software can be uploadedfrom the flash key to the system. Finally, a TERMINAL mode can beselected that is an engineering mode for internal device calibration,system characterization, and system evaluation.

System 10 may also save all information of the device hardware andsoftware as well as the user's input and treatments during operation. Insome embodiments, system 10 has enough memory storage for allinformation saved for at least one year of operation. For example,system 10 may implement 2 MB EEPROM and flexible size memory in someembodiments.

FIGS. 9a-g combine to provide a flow diagram operational method 700 ofultrasonic system 10. In various embodiments, one or more tasks or stepscan be omitted, or intervening tasks or steps can be carried out inaddition those specifically depicted. Operation begins by first poweringon the system at 702, followed by conducting a system self-test at 704.

FIG. 9c shows the steps of self-test 704. First, system 10 can verifythe integrity of the executable code and verifies RTC at 706. Next, at708, if the self-test is passed, operation continues on to 714. If theself-test is not passed, an error message is displayed at 710 on display206 and the system may be shut down at 712. The error message may beused to communicate the issue to customer service.

If 714 is reached (in FIG. 9a ), the number of wounds and size of woundsare input. If a new applicator 80 is present at 716, operation proceeds,if not, a new applicator 80 is loaded at 718. Next, at 720, tuning modecommences.

FIG. 9d shows tuning mode 720. First, the tuning mode voltage is set at722. Next the current loop is set off at 724, followed by a search forthe resonance frequency Fr of ultrasonic transducer 70 at 726. If theresonance frequency is found at 728, the system continues on to 738. Ifthe resonance frequency is not found the system will try again for a setnumber of times at 730. If resonance frequency is not found, after theseattempts, an error is displayed on the system display 206 at 734,followed by system shutdown at 736.

If 720 is reached (in FIG. 9a ), treatment is started following asuccessful tuning mode. Next, at 740, the system checks the RFID tag onthe applicator 80 for a valid state and to ensure that the treatment hasproceeded for less than ninety minutes. If not, treatment is stopped at742 and a new applicator is loaded at 718 before reengaging theoperation at 716. If the RFID tag indicates treatment of less than 90minutes and a valid state at 740, then operation continues on to pumpcontrol at 744.

FIG. 9e shows the pump control 744. First, the system 10 can check thatthe pump door of the peristaltic pump 50 located on the exterior of theconsole/generator unit 50 is closed at 746. If not, the display 206indicates a message to close the pump door at 748. If the pump door isclosed, operation continues to 750 where the pump speed is set. Thesystem then can check the pump speed at 752, and the pump speed is setagain if necessary, before proceeding on to 754 when the pump control iscomplete. In some embodiments, checking pump speed and setting orresetting the speed (e.g., one or both of 750, 752) can be omitted.

When 754 is reached (FIG. 9a ), the current is set for the ultrasonictransducer 70. Next, the operation frequency is set at 756 and thevoltage and current phase is measured at 758. See FIG. 9 b. Next,monitoring the system commences at 760.

FIG. 9f shows monitoring the system at 760. First the system monitors:the temperature of the generator unit 30; the temperature of thetreatment wand 40; the temperature of the case of the ultrasonictransducer 70; the output voltage of the ultrasonic transducer 70; thecurrent of the pump 50; and the communication between the twomicroprocessors 200 and 316 (MCU2 and MCU1). Next, error codes aregenerated and communicated at 764 before returning to 766.

When 766 is reached (FIG. 9b ), if the system is not determined to be inorder, an error message is communicated on the display 206 at 768 andthe system is shut down at 770. If, however, the system is determined tobe ok at 766, the system checks to ensure the voltage/current phaseangle is 0° at 774. If not, operation reverts to 756 in which theoperation frequency is adjusted to so that a voltage/current phase angleof 0° can be achieved. If voltage/current phase angle is set to 0° at772, the system checks to ensure the current sensed is equivalent to thecurrent that was set for the system at 774. If the current does notmatch, operation reverts to 754 and the transducer sets the currentagain before continuing. If the current is appropriate at 774, thesystem then tests to see if the treatment has timed out at 776. If ithas not timed out, operation reverts to 740 and the test of 90 minuteRFID time limit is conducted. If treatment has timed out at 776, thetreatment is stopped at 778 followed by the option to add a furthertreatment or additional time at 780. If another treatment or additionaltime is desired, another treatment is added at 782 and operation revertsto the tuning mode at 720. If no further treatment is desired,information is saved at 784.

FIG. 9g shows saving information 784 in greater detail. First, thesystem collects device setup information, device operation information,and user treatment information at 786. Next, at 788, information issaved to memory (which can be EEPROM or some other memory type or form,such as serial flash or non-volatile in various embodiments) beforecontinuing to system shutdown at 770.

As understood by the various system checks and protocols in thisoperational explanation, the operation of the system can be suspended atmany points. Advantageously, in certain embodiments, both microprocessor200 and microprocessor 316 are configured to individually suspendoperation of the ultrasonic system in fault condition situations. Thisarrangement provides enhanced safety not present in other types ofdesigns.

It should also be appreciated that the exemplary embodiment or exemplaryembodiments are only examples, and are not intended to limit the scope,applicability, or configuration of the invention in any way. Rather, theforegoing detailed description will provide those skilled in the artwith an enabling disclosure for implementing the exemplary embodiment orexemplary embodiments. It should be understood that various changes canbe made in the function and arrangement of elements without departingfrom the scope of the invention as set forth in the appended claims andthe legal equivalents thereof.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. Although the presentinvention has been described with reference to particular embodiments,workers skilled in the art will recognize that changes may be made inform and detail without departing from the spirit and scope of theinvention.

Various modifications to the invention may be apparent to one of skillin the art upon reading this disclosure. For example, persons ofordinary skill in the relevant art will recognize that the variousfeatures described for the different embodiments of the invention can besuitably combined, un-combined, and re-combined with other features,alone, or in different combinations, within the spirit of the invention.Likewise, the various features described above should all be regarded asexample embodiments, rather than limitations to the scope or spirit ofthe invention. Therefore, the above is not contemplated to limit thescope of the present invention.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

1. A non-contact, medical ultrasound therapy system for generating andcontrolling low frequency ultrasound, comprising: a non-contacttreatment wand including an ultrasonic transducer configured to providethe low frequency ultrasound to a patient without contacting thepatient; a generator unit configured to generate electric power outputto drive the ultrasonic transducer to generate and control low frequencyultrasound, the generator unit comprising: a digital frequency generatorand a voltage vs. current phase detector configured to detect a voltagevs. current phase angle, wherein the generator unit is configured toadjust and lock an output frequency of the ultrasonic transducer in aphase-continuous manner based on the voltage vs. current phase angle anddigitally control energy output to the ultrasonic transducer; and acable coupling the non-contact treatment wand to the generator unit. 2.The ultrasound therapy system of claim 1, wherein the system includes afluid delivery mechanism.
 3. The ultrasound therapy system of claim 2,wherein an applicator is coupled to the non-contact treatment wand toapply a fluid.
 4. The ultrasound therapy system of claim 1, wherein thegenerator unit comprises a Direct Digital Synthesis (DDS) chipconfigured to produce a serial resonance frequency that is digitallycontrolled to better than about 0.5 Hz while maintaining constant energyoutput.
 5. The ultrasound therapy system of claim 1, wherein the digitalfrequency generator allows for selection of a frequency between 20 kHzand 50 kHz without hardware modifications.
 6. The ultrasound therapysystem of claim 1, wherein the system allows for parameter control of atleast one of voltage, current, duty cycle and phase angle.
 7. Theultrasound therapy system of claim 1, wherein drive voltage requirementsare less than 50 Vrms for the system.
 8. The ultrasound therapy systemof claim 1, wherein the system is driven at a constant current whichmaintains constant output displacement.
 9. The ultrasound therapy systemof claim 1, wherein the ultrasound therapy system is battery powered.10. An ultrasonic generator unit, comprising: an ultrasonic driver withdigital controls to maintain system displacement at a low ultrasonicserial resonance frequency of a transducer coupled to the ultrasonicgenerator unit, the ultrasonic driver including: a microprocessor, adigital frequency generator controlled by the microprocessor at anoperating frequency, and a voltage vs. current phase detector configuredto detect a voltage vs. current phase angle, wherein the microprocessoris configured to modify the operating frequency based upon the phasedifference to maintain the low ultrasonic serial resonance frequency,and wherein the generator unit is configured to adjust and lock anoutput frequency of the ultrasonic transducer in a phase-continuousmanner based on the voltage vs. current phase angle to digitally controlenergy output of the ultrasonic driver.
 11. The ultrasonic generatorunit of claim 10, wherein the generator unit comprises a Direct DigitalSynthesis (DDS) chip configured to produce a serial resonance frequencythat is digitally controlled to better than about 0.5 Hz whilemaintaining constant energy output.
 12. The ultrasonic generator unit ofclaim 10, wherein selection of a frequency between 20 kHz and 50 kHz ispermitted without hardware modifications.
 13. The ultrasonic generatorunit of claim 10, wherein parameter control of at least one of voltage,current, duty cycle and phase angle is permitted.
 14. The ultrasonicgenerator unit of claim 10, wherein drive voltage requirements are lessthan 50 Vrms.
 15. The ultrasonic generator unit of claim 10, wherein thegenerator unit is driven at a constant current which maintains constantoutput displacement.
 16. The ultrasonic generator unit of claim 10,wherein the generator unit is battery powered.
 17. An ultrasonic systemfor providing non-contact ultrasonic therapy, comprising: a userinterface controlled by a first microprocessor; a treatment deviceincluding an ultrasonic transducer; and a generator unit including anultrasonic driver controlled by a second microprocessor, the generatorunit configured to adjust and lock an output frequency of the ultrasonictransducer in a phase-continuous manner based on a detected voltage vs.current phase angle, wherein both the first microprocessor and thesecond microprocessor are configured to individually suspend operationof the ultrasonic system in a fault condition corresponding to one ormore of: a temperature of the generator unit, a temperature of thetreatment device, a temperature of the ultrasonic transducer, an outputvoltage of the ultrasonic transducer, or a communication failure betweenthe first microprocessor and the second microprocessor.
 18. A method fordigitally generating and controlling low frequency ultrasound used in anon-contact medical ultrasound therapy system, comprising: performing apower on self-test to an ultrasonic therapy system that includes atreatment wand comprising an ultrasonic transducer and a generator unitcomprising an ultrasonic driver; performing a frequency sweep using asine wave to determine a serial resonance frequency of the ultrasonictransducer by identifying a relative minimum impedance of the ultrasonictransducer; adjusting a digital frequency generator output frequencybased on voltage vs. current phase angle to maintain a frequency lockupat the serial resonance frequency; and monitoring voltage and phasedetection circuits of the ultrasonic therapy system for phasedifference.
 19. The ultrasound therapy system of claim 2, wherein thefluid delivery mechanism is a pump.
 20. The ultrasound therapy systemaccording to claim 1, wherein the generator unit phase detector isconfigured to operate such that it is phase continuous at 0° phasedifference between voltage and current.